backtick

Backtick, also called grave accent or backquote, is a punctuation character represented by the ASCII code 96 and rendered as the small ` symbol. It is placed on the keyboard to the left of the 1 key on many layouts, where it is produced unshifted as ` and shifted as ~. Historically, the character originated as a diacritic in typesetting, used in some languages to mark certain vowel qualities or to indicate a grave accent.

In typography and linguistics, the grave accent denotes tone or stress in some languages, and can appear over vowels. The backtick character itself is distinct from the acute, circumflex, or other accents.

In computing, backticks appear in several contexts. In shell scripting, text enclosed in backticks represents a command substitution, where the shell executes the contained command and substitutes its output; many environments now prefer the $(...) syntax due to clarity and nesting. In some programming languages such as Perl, backticks act as an operator that executes a system command and captures its output. In JavaScript, template literals use backticks to create multi-line strings and allow interpolation with the ${expression} syntax.

In SQL dialects, particularly MySQL, backticks are used to quote identifiers that would otherwise be treated as keywords or contain spaces; other systems use double quotes for this purpose.

In markup and documentation, backticks are used to indicate code spans, though this practice is defined by the markup language rather than the character itself.

---